// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_STREAMS_STREAM_H_
#define CONTENT_BROWSER_STREAMS_STREAM_H_

#include <stddef.h>

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "content/browser/byte_stream.h"
#include "content/common/content_export.h"
#include "url/gurl.h"

namespace net {
class IOBuffer;
}

namespace content {

class StreamHandle;
class StreamHandleImpl;
class StreamReadObserver;
class StreamRegistry;
class StreamWriteObserver;

// A stream that sends data from an arbitrary source to an internal URL
// that can be read by an internal consumer.  It will continue to pull from the
// original URL as long as there is data available.  It can be read from
// multiple clients, but only one can be reading at a time. This allows a
// reader to consume part of the stream, then pass it along to another client
// to continue processing the stream.
class CONTENT_EXPORT Stream : public base::RefCountedThreadSafe<Stream> {
public:
    enum StreamState {
        STREAM_HAS_DATA,
        STREAM_COMPLETE,
        STREAM_EMPTY,
        STREAM_ABORTED,
    };

    // Creates a stream.
    //
    // Security origin of Streams is checked in Blink (See BlobRegistry,
    // BlobURL and SecurityOrigin to understand how it works). There's no security
    // origin check in Chromium side for now.
    Stream(StreamRegistry* registry,
        StreamWriteObserver* write_observer,
        const GURL& url);

    // Sets the reader of this stream. Returns true on success, or false if there
    // is already a reader.
    bool SetReadObserver(StreamReadObserver* observer);

    // Removes the read observer.  |observer| must be the current observer.
    void RemoveReadObserver(StreamReadObserver* observer);

    // Removes the write observer.  |observer| must be the current observer.
    void RemoveWriteObserver(StreamWriteObserver* observer);

    // Stops accepting new data, clears all buffer, unregisters this stream from
    // |registry_| and make coming ReadRawData() calls return STREAM_ABORTED.
    void Abort();

    // Adds the data in |buffer| to the stream.  Takes ownership of |buffer|.
    void AddData(scoped_refptr<net::IOBuffer> buffer, size_t size);
    // Adds data of |size| at |data| to the stream. This method creates a copy
    // of the data, and then passes it to |writer_|.
    void AddData(const char* data, size_t size);

    // Flushes contents buffered in the stream to the corresponding reader.
    void Flush();

    // Notifies this stream that it will not be receiving any more data.
    void Finalize(int status);

    // Reads a maximum of |buf_size| from the stream into |buf|.  Sets
    // |*bytes_read| to the number of bytes actually read.
    // Returns STREAM_HAS_DATA if data was read, STREAM_EMPTY if no data was read,
    // and STREAM_COMPLETE if the stream is finalized and all data has been read.
    StreamState ReadRawData(net::IOBuffer* buf, int buf_size, int* bytes_read);

    std::unique_ptr<StreamHandle> CreateHandle();
    void CloseHandle();

    // Returns the status of the stream. This is either an error code that
    // occurred while reading, or the status that was set in Finalize above.
    int GetStatus();

    // Indicates whether there is space in the buffer to add more data.
    bool can_add_data() const { return can_add_data_; }

    const GURL& url() const { return url_; }

    // For StreamRegistry to remember the last memory usage reported to it.
    size_t last_total_buffered_bytes() const
    {
        return last_total_buffered_bytes_;
    }

private:
    friend class base::RefCountedThreadSafe<Stream>;

    virtual ~Stream();

    void OnSpaceAvailable();
    void OnDataAvailable();

    // Clears |data_| and related variables.
    void ClearBuffer();

    bool can_add_data_;

    GURL url_;

    // Buffer for storing data read from |reader_| but not yet read out from this
    // Stream by ReadRawData() method.
    scoped_refptr<net::IOBuffer> data_;
    // Number of bytes read from |reader_| into |data_| including bytes already
    // read out.
    size_t data_length_;
    // Number of bytes in |data_| that are already read out.
    size_t data_bytes_read_;

    // Last value returned by writer_->TotalBufferedBytes() in AddData(). Stored
    // in order to check memory usage.
    size_t last_total_buffered_bytes_;

    std::unique_ptr<ByteStreamWriter> writer_;
    std::unique_ptr<ByteStreamReader> reader_;

    StreamRegistry* registry_;
    StreamReadObserver* read_observer_;
    StreamWriteObserver* write_observer_;

    StreamHandleImpl* stream_handle_;

    base::WeakPtrFactory<Stream> weak_ptr_factory_;
    DISALLOW_COPY_AND_ASSIGN(Stream);
};

} // namespace content

#endif // CONTENT_BROWSER_STREAMS_STREAM_H_
